1. Field of the Invention
The present invention relates to the production of slide fasteners, and more particularly to an apparatus for holding a slider in position during threading or mounting onto a slide fastener chain.
2. Prior Art
An automatic lock slider has a locking pawl that is movable into and out of a guide channel in a slider body in response to pivotal movement of a pull tab. For threading a slide fastener chain through such slider in the manufacture of a slide fastener, the slider must be held in such a manner that the locking pawl is retracted out of the guide channel to allow the passage of the fastener chain through the guide channel.
A known slider holder, as disclosed in U.S. Pat. No. 4,329,778 issued on May 18, 1982, has a support vertically slidably mounted on a base for supporting a slider body upside down, a slit in the support for receiving a pull tab hanging from the slider body, and a locking ball carried by the base, the support being normally urged upwardly by a (first) spring which is relatively strong. The ball is movable on the base between a slider-holding position in which the ball projects into the slit for engagement with the edge of an opening in the pull tab, and a slider-release position in which the ball is retracted out of the slit for releasing the pull tab. The ball is normally urged to the slider-holding position by a (second) spring. However, this prior holder is not satisfactory because of the following problems:
1. The degree of firmness of the engagement between the ball and the pull tab varies depending on the size of the pull tab's opening.
2. If the second spring is strong, it is not easy to insert the pull tab into the slit. On the contrary, if the second spring is weak, adequate engagement between the ball and the pull tab is difficult to achieve. In the latter case, if the first spring is considerably strong, the pull tab tends to accidentally come off the ball as the support is moved upwardly due to undue resilience of the first spring. Accordingly, it is necessary to control the resilience of each spring, which is laborious.
3. There is considerable resistance by the spring-biased ball when the slider is removed from the holder.
4. In order to have adequate engagement between the ball and the pull tab, an auxiliary spring is necessary for assistance to the second spring in urging the ball.